A common practice in the packaging of insulation mats of fibrous mineral material is to compress the insulation material to a small fraction of its former size, and then package the compressed material in a bag or a roll form. It is important that when the package of insulation material is opened and the insulation material is released from compression, that the material expand to a predetermined thickness. Accordingly, it is a common practice in the manufacture of insulation materials to periodically select and open sample insulation packages in order to assess the expansion of the insulation mat. The measurement of the thickness, and hence the expansion, of the samples is accomplished using a tool known as a pin gauge or depth gauge. The pin gauge is a calibrated rod or stick upon which a disc is slideably mounted. Use of the pin gauge involves placing the stick into the insulation mat until the stick penetrates the mat through to the floor or work surface, and then sliding the disc down to the surface of the mat. Upon removal of the stick from the mat, a measurement of the thickness of the mat can be read from the stick. The method of measuring the thickness of mats with a pin gauge is described in ASTM Standard C 167-64.
One of the problems in measuring the expansion of insulation samples with the pin gauge is that it is burdensome to take repeated measurements of the thickness of the sample over the 24 to 30 hour time period required for such measurements. Another significant problem with pin gauge measuring is the inconsistency of measurements taken by different users. The subjectivity involved in using the pin gauge can result in different measurements of the same insulation material by different operators. The method and apparatus of the invention are directed towards the solution of the above problems.